BEIRUT — An advance group of international inspectors arrived in Syria on Tuesday to begin the ambitious task of overseeing the destruction of President Bashar Assad’s chemical weapons program, kicking off a mission that must navigate the country’s bloody civil war as well as the international spotlight.

Twenty inspectors from a Netherlands-based chemical weapons watchdog crossed into Syria from neighboring Lebanon on their way to Damascus to begin their complex mission of finding, dismantling and ultimately destroying an estimated 1,000-ton chemical arsenal.

The experts have about nine months to complete the task, which has been endorsed by a U.N. Security Council resolution that calls for Syria’s chemical stockpile to be eliminated by mid-2014. It is the shortest deadline that experts from the Organization for the Prohibition of Chemical Weapons have ever faced in any nation, and their first mission in a country at war.

The team arrived in Damascus late Tuesday afternoon in a 19-vehicle convoy that was escorted from the border by two representatives from the Syrian Foreign Ministry. The inspectors were expected to meet with officials from the ministry later in the day.

Experts at The Hague, where the OPCW is based, said Sunday the inspectors’ priority is to achieve the first milestone of helping Syria scrap its ability to manufacture chemical weapons by a Nov. 1 deadline, using every means possible. That may include smashing mixing equipment with sledgehammers, blowing up delivery missiles, driving tanks over empty shells or filling them with concrete, and running machines without lubricant so they seize up and become inoperable.

Some of the inspectors will be double-checking Syria’s initial disclosure of what weapons and chemical precursors it has and where they are located. Others will begin planning the logistics for visits to every location where chemicals or weapons are stored.

Within a week, a second group of inspectors is scheduled to arrive — fewer than 100 combined — and form teams that will fan out to individual sites. Their routes are secret — both for their safety and because Syria has the right not to reveal its military secrets, including base locations.

The inspectors’ mission was born out of a deadly chemical attack on opposition-held suburbs of Damascus on Aug. 21. The U.S. and its allies accuse the Syrian regime of being responsible, while Damascus blames the rebels.